Hollow carbon electrode

ABSTRACT

A hollow electrode with a longitudinal passage therethrough which consists of carbon material and in which the surface of the passage is made substantially gas-impermeable.

United States Patent Inventors Appl. No. Filed Patented Assignee Priority Kurt Kegel Essen-Steele;

Dleter Zollner, Erlangen; Bernhard Reichelt, Nuruberg-Laufamholz; Konrad Kozlol, Rothenbach an der Pegnitz, Germany May 19, 1969 June 28, 1971 C. Conradty Nurnberg, Germany May 24, 1968 Germany HOLLOW CARBON ELECTRODE 11 Claims, 4 Drawing Figs.

U.S. Cl 13/18 Int. Cl 1105b 7/06 [50} FieldofSearch 13/l8,20, 31; 117/228; 314/60 [56] References Cited UNITED STATES PATENTS 1,912,560 6/1933 Wiles 13/18 2,817,605 12/1957 Sanz et a1 13/20X 2,911,319 11/1959 Peter ll7/228X 3,105,864 10/1963 Robinson l3/18X 3,120,453 2/1964 Fitzer et a1 13/18X 3,365,5 3'3 l/l968 Alexander 13/18 Primary Examiner-Bernard A. Gilheany Assistant Examiner Roy N. Envall, Jr. A!t0rneyWalter Becker ABSTRACT: A hollow electrode with a longitudinal passage therethrough which consists of carbon material and in which the surface of the passage is made substantially gas-impermeable.

PATENTEUJUNZMQYI 3,588,307

' F|G.3 FIGA HOLLOW CARBON ELECTRODE In electrothermal processes, especially in connection with the production of electrosteel, it is known to employ hollow or wick electrodes because the annular design of the electrode ends stabilizes the electric arc.

It is also known by introducing ionizing gases, as for instance argon, nitrogen, and the like, to bring about a further increase in the stabilization of the electric arc and to considerably improve the burning conditions of the electric arc inasmuch as the thermal degree of efficiency is increased and an unfavorable efiect upon the network is reduced while, above all, the life of the fire resistant lining which considerably contributes to the costs of the electrosteel is materially extended.

Inherent to the manufacturing process of the electrodes, due to the disintegration of the binding agent, a certain porosity is obtained through the entire structure of the electrode. A portion of the gas introduced under a certain pressure escapes through these pores and is lost so that it will not be available at the burning end of the electrode for the stabilization of the electric arc. Therefore, numerous but vain attempts have been made to eliminate these losses since the employed gases, as for instance argon, are rather expensive.

It is, therefore, an object of the present invention to provide a hollow carbon electrode (the term also includes graphite) which will eliminate the loss of ionizing gases.

It is also an object of the present invention to provide a hollow electrode as set forth in the preceding paragraph, which will avoid gas loss and thus the pressure drop in the electrode which pressure drop disadvantageously affects the operation of the electrode.

These and other objects and advantages of the invention will appear more clearly'from the following specification in connection with the accompanying drawing, in which:

FIG. I diagrammatically illustrates a hollow or tubular carbon electrode having its interior wall surface sealed in conformity with the present invention.

FIG. 2 is an enlargement of an interior portion of an electrode according to the invention in which the inner wall of the graphite electrode is made gas-impermeable by SiO FIG. 3 shows a cutoutof the interior portion of a graphite electrode having its interior wall surface made gas-impermeable by a metallic coating.

FIG. 4 is a further embodiment of the invention according to which a tubular graphite electrode has its interior wall surface sealed by a metallic tube firmly pressed thereinto.

The hollow electrode of carbon material according to the present invention for the introduction of gases for the stabilization of the electric arc is characterized primarily in that the inner wall surface is sealed or made gas-impermeable.

More specifically, according to the present invention, the inner surface 1 of the tubular electrode 2 is sealed with substances 3 which during a thermal treatment under the exclusion of air will coke while having properties similar to those of the electrode material. Such substances are well known in connection with impregnating methods for carbon or graphite material and such substances are in particular tar and tar products, such as pitch, and also synthetic resins, sugar solution, water glass solution, or the like. In the last mentioned instance, a filling of the pores with silicic acid will increase the desired effect. Depending on the desired degree of compacting, the said substances are caused to penetrate into the electrode body to a greater or lesser extent. Such sealing of the inner wall surface of the axial bore of the electrode is shown in FIGS. 1 and 2. Particularly effective as far as the sealing of the inner surface I ofthe hollow electrode is concerned, is the formation of pyrolytic carbon from the gaseous phase.

Extensive research in connectionwith the present invention has shown that also other suitable materials will bring about the desired effect. Thus, for instance, it is possible, in conformity with the present invention, to cover the inner surface 1 of the hollow electrode by a metallic coating 4 as shown in FIG. 3. Depending on the magnitude of the inner axial bore of the electrode and the required sealing effect, the thickness of the metallic skin will be selected. T e metallic skin may be deposited electrolytically or by disintegration of organic metallic compounds.

According to a further modification of the invention as illustrated in FIG. 4, the inner wall surface of the electrode 2 is covered by a metal pipe 5 which is firmly pressed into the bore of the electrode. If desired, the metal pipe may also be replaced by a pipe of carbon material which has been sealed prior to its insertion into the electrode.

In conformity with a further development of the present invention, a still further improvement has been obtained by inserting oriented substances. In this connection, for instance, KBF K WC, TiC have proved effective as sealing material while additionally having a stabilizing effect on the electric are.

It is, of course, to be understood that the present invention is, by no means, limited to the particular showing in the drawing and the materials set forth above but also comprises any modifications within the scope of the appended claims. Thus, other ionizing substances with similar or better effects may be employed. It is also to be understood that as sealing mass a fire resistant material may be employed by means of which the surface of the central passage is coated. In this connection reference is made to the Torkrett method.

We claim:

l. A hollow electrode of carbon material for the introduction of gases for stabilizing the electric are, which has a longitudinal passage therethrough, and in which the inner wall of the electrode body is sealed so as to make the same substantially gas-impermeable, there being a means to supply gas and direct it through the electrode rendered gas impervious.

2. An electrode according to claim 1, in which the inner surface of the electrode is sealed by substances adapted to be coked, said substances being selected from the group consisting of tar, pitch, synthetic resin and sugar solution.

3. An electrode according to claim 1, in which the pores on the inside of the electrode are sealed by silicic acid and the inner surface of the electrode is covered by water glass solutron.

' 4. An electrode according to claim 1, in which the inner surface of the electrode is coated with a fire resistant material.

5. An electrode according to claim I, in which the inner surface of the electrode is sealed by the formation of pyrolytic carbon from the gas phase.

6. An electrode according to claim 5, in which as pyrolytic carbon material is used a substance selected from the group consisting of hard carbon and pyrographite.

7. An electrode according to claim 1, in which the inner surface of the electrode is sealed by a metallic coating.

8. An electrode according to claim 1, in which the inner surface of the electrode is sealed by a pipe having a gas-impermeable inner surface. a

9. An electrode according to claim 8, in which said pipe is a pipe consisting of carbon material.

10. An electrode according to claim 8, in which said pipe is a metallic pipe. I

II. An electrode according to claim 1, in which the sealed inner surface of the electrode contains substances adapted to stabilize the electric are, said substances consisting of ionizing material selected from the group consisting of KBE, K 80 WC, TiC. 

